McKeown P, Davidson M G, Lowe J P, Mahon M F, Thomas L H, Woodman T J, Jones M D
Doctoral Training Centre in Sustainable Chemical Technologies, University of Bath, Bath BA2 7AY, UK and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK.
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK.
Dalton Trans. 2016 Mar 28;45(12):5374-87. doi: 10.1039/c5dt04695e.
Herein we report the synthesis and characterisation of a series of salalen and salan ligands derived from 2-(aminomethyl)piperidine. Depending on the choice of starting salicylaldehyde, a bicyclic salan type ligand (1-3H2) or imino salalen type ligand (4-6H, 7-9H2) were prepared. The ligands were successfully complexed to group 4 metals and aluminium; with hafnium and zirconium octahedral complexes, M(1-3)2, were realised; whilst with aluminium tetrahedral and trigonal bipyramidal complexes, Al(1-9)Mex (x = 1,2), were isolated. The complexes have been characterised in solution via(1)H and (13)C{(1)H} NMR spectroscopy and in the solid state by X-ray crystallography. The group 4 complexes were observed to have a fac-fac arrangement of ligands and there were two isomers present when 3H2 was ligated. The imino aluminium complexes Al(7-9)Me were isolated as a mixture of diastereoisomers. The resultant complexes were trialed in the ring opening polymerisation of rac-lactide with both heterotactic and isotactic PLA being demonstrated. Tacticity was found to be dependent on the nature of the ligand and metal used; the M(1-3)2 complexes were generally found to have a heterotactic preference (Pr = 0.67-0.76) and the aluminium polymerisation outcome was dictated more by the steric influence of the ligand, particularly for Al(4/6)Me2/Al(7/9)Me.
在此,我们报告了一系列源自2-(氨甲基)哌啶的水杨醛缩邻氨基酚和三齿氮配体的合成与表征。根据起始水杨醛的选择,制备了双环三齿氮型配体(1 - 3H₂)或亚氨基水杨醛缩邻氨基酚型配体(4 - 6H, 7 - 9H₂)。这些配体成功地与第4族金属和铝形成配合物;实现了八面体配合物M(1 - 3)₂,其中M为铪和锆;同时分离出了四面体和三角双锥铝配合物Al(1 - 9)Meₓ (x = 1,2)。通过¹H和¹³C{¹H}核磁共振光谱对溶液中的配合物进行了表征,并通过X射线晶体学对固态配合物进行了表征。观察到第4族配合物的配体呈面-面排列,当连接3H₂时存在两种异构体。亚氨基铝配合物Al(7 - 9)Me以非对映异构体混合物的形式被分离出来。所得配合物用于外消旋丙交酯的开环聚合试验,证明了可得到间同立构和全同立构的聚乳酸。发现立构规整度取决于所用配体和金属的性质;通常发现M(1 - 3)₂配合物具有间同立构偏好(Pr = 0.67 - 0.76),铝聚合的结果更多地由配体的空间影响决定,特别是对于Al(4/6)Me₂/Al(7/9)Me。